In a passive optical communication network, signals from a central office are transmitted through one or more coupling elements to as many as 64 optical network unit (ONU) receivers. Conventional monitoring techniques cannot readily be used to identify faults on individual fibers since the inputs and outputs from each ONU distribution fiber are conventionally multiplexed onto the same feeder fiber going to the central office. Optical time domain reflectometry (OTDR) has, in fact, been used to locate anomalous losses in passive optical networks. However, means have been generally unavailable for identifying features in the received OTDR signals with particular distribution fibers with adequate specificity. Moreover, coupling losses in conventional networks have reduced the sensitivity of OTDR techniques, placing large demands on the power of OTDR laser transmitters.